/* vi: set expandtab sw=4 sts=4: */
/* hash.c - hash tables for opkg

   Steven M. Ayer, Jamey Hicks

   Copyright (C) 2002 Compaq Computer Corporation

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2, or (at
   your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.
*/

#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "hash_table.h"
#include "opkg_message.h"
#include "xfuncs.h"

static unsigned long djb2_hash(const unsigned char *str)
{
    unsigned long hash = 5381;
    int c;
    while ((c = *str++))
        hash = ((hash << 5) + hash) + c;        /* hash * 33 + c */
    return hash;
}

static int hash_index(hash_table_t * hash, const char *key)
{
    return djb2_hash((const unsigned char *)key) % hash->n_buckets;
}

/*
 * this is an open table keyed by strings
 */
void hash_table_init(const char *name, hash_table_t * hash, int len)
{
    if (hash->entries != NULL) {
        opkg_msg(ERROR, "Internal error: non empty hash table.\n");
        return;
    }

    memset(hash, 0, sizeof(hash_table_t));

    hash->name = name;
    hash->n_buckets = len;
    hash->entries = xcalloc(hash->n_buckets, sizeof(hash_entry_t));
}

void hash_print_stats(hash_table_t * hash)
{
    printf("hash_table: %s, %d bytes\n"
           "\tn_buckets=%d, n_elements=%d, n_collisions=%d\n"
           "\tmax_bucket_len=%d, n_used_buckets=%d, ave_bucket_len=%.2f\n"
           "\tn_hits=%d, n_misses=%d\n", hash->name,
           hash->n_buckets * (int)sizeof(hash_entry_t), hash->n_buckets,
           hash->n_elements, hash->n_collisions, hash->max_bucket_len,
           hash->n_used_buckets,
           (hash->n_used_buckets ? ((float)hash->n_elements) / hash->n_used_buckets : 0.0f),
           hash->n_hits, hash->n_misses);
}

void hash_table_deinit(hash_table_t * hash)
{
    unsigned int i;
    if (!hash)
        return;

    /* free the reminaing entries */
    for (i = 0; i < hash->n_buckets; i++) {
        hash_entry_t *hash_entry = (hash->entries + i);
        free(hash_entry->key);
        /* skip the first entry as this is part of the array */
        hash_entry = hash_entry->next;
        while (hash_entry) {
            hash_entry_t *old = hash_entry;
            hash_entry = hash_entry->next;
            free(old->key);
            free(old);
        }
    }

    free(hash->entries);

    hash->entries = NULL;
    hash->n_buckets = 0;
}

void *hash_table_get(hash_table_t * hash, const char *key)
{
    int ndx = hash_index(hash, key);
    hash_entry_t *hash_entry = hash->entries + ndx;
    while (hash_entry) {
        if (hash_entry->key) {
            if (strcmp(key, hash_entry->key) == 0) {
                hash->n_hits++;
                return hash_entry->data;
            }
        }
        hash_entry = hash_entry->next;
    }
    hash->n_misses++;
    return NULL;
}

int hash_table_insert(hash_table_t * hash, const char *key, void *value)
{
    unsigned int bucket_len = 0;
    int ndx = hash_index(hash, key);
    hash_entry_t *hash_entry = hash->entries + ndx;
    if (hash_entry->key) {
        if (strcmp(hash_entry->key, key) == 0) {
            /* alread in table, update the value */
            hash_entry->data = value;
            return 0;
        } else {
            /*
             * if this is a collision, we have to go to the end of the ll,
             * then add a new entry
             * before we can hook up the value
             */
            while (hash_entry->next) {
                hash_entry = hash_entry->next;
                if (strcmp(hash_entry->key, key) == 0) {
                    hash_entry->data = value;
                    return 0;
                }
                bucket_len++;
            }
            hash_entry->next = xcalloc(1, sizeof(hash_entry_t));
            hash_entry = hash_entry->next;
            hash_entry->next = NULL;

            hash->n_collisions++;
            if (++bucket_len > hash->max_bucket_len)
                hash->max_bucket_len = bucket_len;
        }
    } else
        hash->n_used_buckets++;

    hash->n_elements++;
    hash_entry->key = xstrdup(key);
    hash_entry->data = value;

    return 0;
}

int hash_table_remove(hash_table_t * hash, const char *key)
{
    int ndx = hash_index(hash, key);
    hash_entry_t *hash_entry = hash->entries + ndx;
    hash_entry_t *next_entry = NULL, *last_entry = NULL;
    while (hash_entry) {
        if (hash_entry->key) {
            if (strcmp(key, hash_entry->key) == 0) {
                free(hash_entry->key);
                if (last_entry) {
                    last_entry->next = hash_entry->next;
                    free(hash_entry);
                } else {
                    next_entry = hash_entry->next;
                    if (next_entry) {
                        memmove(hash_entry, next_entry, sizeof(hash_entry_t));
                        free(next_entry);
                    } else {
                        memset(hash_entry, 0, sizeof(hash_entry_t));
                    }
                }
                return 1;
            }
        }
        last_entry = hash_entry;
        hash_entry = hash_entry->next;
    }
    return 0;
}

void hash_table_foreach(hash_table_t * hash,
                        void (*f) (const char *key, void *entry, void *data),
                        void *data)
{
    unsigned int i;
    if (!hash || !f)
        return;

    for (i = 0; i < hash->n_buckets; i++) {
        hash_entry_t *hash_entry = (hash->entries + i);
        do {
            if (hash_entry->key) {
                f(hash_entry->key, hash_entry->data, data);
            }
        } while ((hash_entry = hash_entry->next));
    }
}
